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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cf771e9absm15606825e9.9.2026.09.03.14.48.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 14:48:06 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , Nicholas Carlini , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf v1 5/8] bpf: Mark faultable stack helpers as sleepable Date: Thu, 3 Sep 2026 23:47:51 +0200 Message-ID: <20260903214758.2727663-6-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260903214758.2727663-1-memxor@gmail.com> References: <20260903214758.2727663-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1899; i=memxor@gmail.com; h=from:subject; bh=eCoblO1wa9iyl/6H9+QTh1GDpRn8Bp6BkAtxW2LCWDg=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIWvma1bBb23P/JbcV179+Eu1SVoCx8bTZ3M4N0+66jfl/ ZodLgaTO0pZGMS4GGTFFFlK/u9jMj5R+TvQdhk3zBxWJpAhDFycAjCRCB5Ghg1hjtbflCec3nZC /gSTXfvazJ0OAr3/ODZEmu6xjOD7foCR4W02/zOdtlKnZZJVJses05QKn07bkup6VKpAuIBRndm IHQA= X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit The faultable variants of bpf_get_stack() and bpf_get_task_stack() pass may_fault=true into the common stack collection code. Resolving user-space build IDs may then call build_id_parse_file() and block on filesystem reads. Neither helper prototype sets might_sleep. Since prototype selection uses the sleepability of the whole program, the verifier can still allow these helpers from a non-sleepable region within that program, such as an explicit RCU or preemption-disabled region. The task-stack helper can also be called from a non-sleepable timer callback of a sleepable program. Mark both faultable prototypes as sleepable. The existing helper context check then rejects these calls while continuing to allow them in genuinely sleepable contexts. Fixes: d4dd9775ec24 ("bpf: wire up sleepable bpf_get_stack() and bpf_get_task_stack() helpers") Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/stackmap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index a839041e0d00..d09d4c3fe547 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -875,6 +875,7 @@ BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, si const struct bpf_func_proto bpf_get_stack_sleepable_proto = { .func = bpf_get_stack_sleepable, .gpl_only = true, + .might_sleep = true, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_CTX, .arg2_type = ARG_PTR_TO_UNINIT_MEM, @@ -928,6 +929,7 @@ BPF_CALL_4(bpf_get_task_stack_sleepable, struct task_struct *, task, void *, buf const struct bpf_func_proto bpf_get_task_stack_sleepable_proto = { .func = bpf_get_task_stack_sleepable, .gpl_only = false, + .might_sleep = true, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_BTF_ID, .arg1_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], -- 2.53.0